backup computer

[gamon]

If you're solo diving inside NDLs, all you need are two computers basically acting as a depth gauge and a bottom timer.

No clue what this means but it sounds wrong.

 

[DiveLikeAMuppet]

No clue what this means but it sounds wrong.

If you are diving 32% as god intended (tm), all you need to know to stay within NDL on a recreational dive is your max (average if aggressive) depth and runtime, follow the right rule of thumb and then ascent safely based on your training.

 

[Divin'Papaw]

I've been diving with 2 computers for years. I have 2 of the same computer, setup identically. I also have a 3rd computer which I can use if either of those are out of service.

For me it is Shearwater. I've been a user of their computers since 2012. I dive 2 Perdix 2s and I also have a Peregrine (non-Tx) available if needed. They all run the same algorithm and I have them configured with the same fundamental settings. But exactly which brand is pretty irrelevant. As long as you are using one of the numerous high quality brands today.

I'm a believer in the old tech diving adage ... 2 is 1 and 1 is none.

 

[gamon]

If you are diving 32% as god intended (tm), all you need to know to stay within NDL on a recreational dive is your max (average if aggressive) depth and runtime, follow the right rule of thumb and then ascent safely based on your training.

I respectfully disagree and will stick with my dive computer as the most effective way to monitor my remaining ndl time rather than winging it with rules of thumb.

At the very least, your strategy is only effective for a relatively square profile, in any other scenario you are either risking overstaying at depth or unnecessarily limiting your bottom time.

 

[LFMarm]

2 identical computers to ensure same algorithm and screen layout.

 

[Allen-1]

For technical or solo diving, I'd go with two of the same computers, or two with the same algorithms and settings.

I'm not doing technical or solo diving - I'm doing warm water recreational diving with a buddy. For that, I have an air-integrated G3 as my primary. I have a SPG clipped to my left upper ring, and a backup dive computer, (not a G3), on my non-dominant wrist.

If my primary computer fails - I still have at least four critical data points available:
remaining gas
current depth
MOD
Ascent (or descent) rate

If my primary fails - I'm calling the dive, and using the working tools to do a "normal" ascent and safety stop.
Diving recreationally, up to four tanks a day for multiple days, I've not had my more conservative backup DC lock me out or give me issues - other than one mildly irritating known one:
My G3 starts safety stop at 15' and if I dip back down below 20, it stops it and resumes dive.
My backup DC, (Suunto D5), starts safety stop at 20'.

 

[1070man]

One important thing I read once. If one fails, and you’re doing multiple dives, you might be done for the day. If you have a backup then you should be able to finish dives for the day. Like someone else pointed out, if you were on a liveaboard.

 

[andrespp]

It depends on context: OC, CC. OW, solo, big vs small deco.....

 

[Dsix36]

Most of the previous responses are spot on but I would like to add one recommendation that I firmly believe in. It has made my life (by possibly avoiding death on a very bad day) much easier. I dive with 2 identical computers with all settings matched. I do this for the obvious reasons stated above but also to make sure that I have the muscle memory to use the secondary computer properly in the event of a failure. Not all failures are equal and if it happens on a very bad day, then your mental abilities will be impaired due to the stress induced. Having a backup computer that you are 100% comfortable and familiar can make a huge difference in your outcome.

 

[scrane]

I dive a Perdix and a Garmin Descent Mk1. They both use Buhlmann and track very closely. I like the Garmin because it gives me tactile alarms for ascent rate and a Nitrogen loading graph for quick reference.